The end-Permian mass extinction saw a loss of 90% of the
species in the ocean and about 70% of vertebrate families on land (Erwin
1994).† The event is dated at 251 million
years ago.† The precise timing and how
long the extinction event lasted are still being debated.† However, the end-Permian mass extinction was
geologically a rapid event (~800,000 years).†
There is no conclusive evidence of a huge extraterrestrial impact
similar to the one that caused the extinction of the dinosaurs.† Currently the scientific community believes
that it was a combination of events that caused the mass extinction and plate
tectonics played an important role.†

From USGS website.

Pangaea

Pangaea at the time of the Permian extinction extended
from pole to pole.† It was formed
~300,000 million years ago by the collision of Laurasia from the north and
Gondwana from the south.† It was
surrounded by the superocean Panthalasa.†
Pangaea broke up about ~200 million years ago.† At the time of the mass extinction, Pangaea
produced glaciation, created change in regional and global climates and caused
marine regression.†

Marine Regression

During the marine regression Pangaea continental shelves
were exposed to the atmosphere, negatively affecting the habitat of marine
organisms.† The sea level can decrease
for different reasons.† At the time of
the Permian mass extinction Pangaea was at its maximum packing resulting in a
lower sea level.† This was caused when
landmasses that formed Pangaea collided, compressing and thickening the
supercontinentís crust.† It resulted in a
smaller landmass and a larger ocean basin for the Earthís fixed amount of
water.† Thermal uplift of Pangaea could
have lowered the sea level in relation to the supercontinent.† Heat could have accumulated underneath
Pangaea, thermally uplifting the landmass in relation to the surrounding
ocean.†

Climates

The climate during the Permian mass extinction
was affected by the size of Pangaea and the decrease of carbon dioxide in the
atmosphere.† Coastal area was lost when
the continents reassembled to form Pangaea.†
A large percentage of mild moist coastal environments were replaced by a
large arid interior climate.† Pangaea
spanned all latitudes, but did not have the range of climates that are found on
Earth today.† Pangaea blocked the flow of
equatorial ocean currents, combined with the relatively high elevation along
the western side caused the interior to be cool and dry (Rogers 2004, pg
173).† Carbon dioxide in the atmosphere
helps the Earth to retain heat.† During
periods of low sea level, large amount of silicate minerals are eroded from
continental crust and carried to the oceans by rivers.† These silicate minerals combine with carbon
dioxide in seawater and produce solid precipitates.† When carbon dioxide is drawn down into ocean
sediments, there is less carbon dioxide in the atmosphere and the Earth cools
forming glaciers near the poles.†

Near view of glacial polish, striae and chatter marks,

developed by Permian ice on Proterozoic quartzite.

Ice moved toward upper right.†
Hallet Cove. Hammer for scale.

South Australia. n.d.†
(from USGS website)

Glaciation

During the time of the Permian extinction
Pangaea stretched from pole to pole providing an opportunity for glaciers to
form.† The water trapped in the glacier
ice lowers the sea level even more and also drives the heat engine of ocean
vertical currents between the tropics and the poles.† There is evidence that glaciers formed over
the south pole and possible the north pole at the time of the Permian
extinction.†

Location of Siberian Traps

(Image from USGS
website)

Siberian Traps

The Siberian Traps represents one of the largest flood
basalt provinces on Earth and erupted 251 million years ago over a time
interval of about 900,000 years.† The
eruptions spewed 2-3 million cubic kilometers of basalt lava, covering 3.9 million
square kilometers to a depth of 400 to 3000 meters.† It was so large and violent that it could
have caused worldwide atmospheric contamination by injecting vast amounts of
dust and sulphate gases into the atmosphere.†
The world climate could have been affected with the addition of volcanic
gasses in the atmosphere (Benton 2003, pg 262).†

Summary

Currently
there is no single agreed upon event that caused the Permian mass
extinction.† It is believed that a
combination of factors caused the worst mass extinction the world ever
experienced.† Environmental pressure on
organisms caused by plate tectonics seems to have played an important
role.† The combination of a single supercontinent
affecting climate, glaciation and sea level with the additional environmental
stress of the Siberian Traps may have been the driving force that nearly wiped
out life on Earth.